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This answer: How to check if a fence or cable has electricity without having special tools? gives some unsafe advice for checking to see if a power cable is energized or not. In particular:

On that thought, I do recall spitting on an electric wire having some effect. If you get water on the wire, it may sizzle or make some other sound if there's a significant enough of a current flowing through it, but only if there is a significant amount of current.

and

a COMPASS which you could use to check for an electrical current. Hold the compass near the wire, the magnetic field will move the needle if there is a current in the wire.

While the compass technique may be able to detect current flowing through a wire under some conditions (it generally only works with DC current, the magnetic field from AC fluctuates so rapidly that the needle can't keep up), there's no reason to believe that spitting on the wire can do so. And current flow is not the same as danger, if there's a metal object sticking out of an electrical outlet, there will be no current flowing through it, but if you grab it, you can still be electrocuted because there will be current flowing through you. A downed cable in the wilderness is likely to be broken, but one (or both) of the broken ends may still have a lethal voltage potential with no current flowing at all - something has to complete the circuit for current to flow, and ideally that "something" won't be a person.

If someone trusts this advice to check the safety of an electrical cable found in the wilderness, he may be in for a shock (literally) when he grabs an energized wire after his compass told him it was safe.

The question itself is a little dubious, since one shouldn't trust random wires/cables to support your weight when climbing up or down a cliff, but I suppose in some survival situations it may be necessary. The safety (or lack thereof) of using a found cable is mentioned in the answer I linked to, so I'm really just questioning the validity of his methods to test the cable to see if it's live.

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  • Why the downvote? Is there some question over whether or not spitting on a wire can tell you if it's safe to touch?
    – Johnny
    Dec 4, 2014 at 19:46

2 Answers 2

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    I generally agree except with #3. You shouldn't edit someone else's answer to "correct" it unless it was a obviously unintended error, like a typo, by the original author. Otherwise, that author has the right to say what he thinks is correct, and you have the right to disagree by downvoting commenting, and/or writing your own answer. You do NOT have the right to make the original author appear to say something he didn't intend.
    – Olin Lathrop
    Dec 8, 2014 at 15:08
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This has been brought up already over on Electrical Engineering as it is a much more common problem there.

Quick summary of the top answer:

I don't think that we should have restrictions on electronics which are perceived to be dangerous.

Of course, we need to use judgement. If the asker demonstrates a callous lack of disregard for safety, a "send me teh codez" attitude, or a desire to create something violent, we should use stronger language to communicate the danger of the operation. However, I don't think we should exclude questions about these topics.

Finally, what does "dangerous" mean? If 120V wall power is dangerous, is 60V also dangerous? What if there's a fuse? This could soon devolve into "Nothing over 24V and 500mA!"

So really it comes down to usual practice on Stack Exchange - which is what ShemSeger says in his answer.

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    The discussion there is "Should we allow questions on dangerous stuff?". The topic here is "What to do about an unsafe answer?" - unrelated.
    – anatolyg
    Feb 17, 2015 at 17:28

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